Purification of beta-lactoglobulin from whey protein concentrate by pepsin treatment

beta-Lactoglobulin was purified from whey protein concentrate by a combination of pepsin treatment and membrane filtration. Porcine pepsin was added to whey protein (1:200, wt/wt), and the mixture was then incubated at pH 2.0 and 37 degrees C for 60 min. The protein fraction was collected by ammonium sulfate precipitation, and the precipitate was either dialyzed against water using a dialysis membrane (20-kDa pore size) or filtered using an UF membrane (30-kDa pore size). The beta-LG did not differ from standard beta-LG as measured by chromatography, SDS-PAGE, native PAGE, differential scanning calorimetry, or UV spectrum. Based on the results, a simplified procedure was developed, consisting of pepsin treatment and UF, to purify beta-LG directly from whey.